The discovery in the 1980s that the gaseous signaling molecule nitric oxide regulates blood vessel dilation and blood flow revolutionized biomedical research, leading most famously to new drugs for erectile dysfunction such as Viagra. Yang et al. provide evidence that vascular function is also controlled by hydrogen sulfide (H2S), the same gas that is responsible for the smell of rotten eggs and that recently has been shown to induce a hibernation-like state in animals. Mice genetically deficient in cystathionine γ-lyase, an enzyme that produces H2S, developed age-related hypertension, and their blood vessels showed an impaired response to treatments that promote vasorelaxation. Thus, like nitric oxide, H2S regulates blood pressure—a finding that could pave the way toward new treatments for vascular disorders.